If you are going to put the effort into repairing your flute, then you should use high quality materials. Most kits that I’ve seen on the Internet include low grade pads. If you put a low grade pad in your flute, getting the flute to play well is extremely difficult if not impossible. It is possible that the instrument will sound worse with these pads. The biggest investment in flute repair is your time so don’t short-change your time with bad parts and materials.
If you want to get into flute repair, read two books: Theobold Boehm’s “The Flute and Flute Playing” and Jim Phelan’s “The Complete Guide to the Flute”. You should also have prior experience working with tools and fixing things. If you also need to learn basics of mechanical repair, then practice first on larger objects. Flutes and piccolos present their own difficulties by virtue of having such small parts. The tools used for flutes and piccolo are small and specialized and not easily come by. You will need access to suppliers of jewerly, watch, or instrument repair equipment.
Then you should ideally work with someone who has experience with repair. No two repairpeople approach problems the same way or use the same techniques or materials. If you learn from more than one person, then you have that much more exposure to differing methodologies and tools. How to find this person or business is your own process.
Finally, you should learn how to play test an instrument. This is different than playing your own instrument. Play testing means finding all the obvious and not so obvious problems that can crop up in an instrument. You should also learn to play with as light a touch as possible to test to see that the adjustments are to extremely precise tolerances. If you aren’t interested in doing flute repair for others, then you only need to learn how to test your instrument to your own playing tolerances.